This invention relates to flow control valves, and more particularity, to a needle valve having a deformable seal that sets against and seals against the needle when the needle is moved to the closed position and where the normal hard seat prevents the needle from overly deforming the deformable seal.
Needle valves are used in a wide variety of applications where precision and accuracy are needed in controlling the flow of a fluid. In such typical current needle valves, the needle is a tapered member that is rotated by the user and such rotation causes the needle to move with respect to its seat by virtue of a threaded engagement of the needle with the valve housing. As the needle moves with respect to its seat, the flow of the fluid is controlled.
It is obviously important, therefore, that the needle be sealed in its closed position against the valve housing so that there is no leakage through the valve. Various types of seals have been used in such valves, some of which are part of the needle itself and are deformable or pliant and which seal against the internal hard surface of the valve passageway.
Other seals are affixed to the internal surface of the valve passageway but are secured by complex and expensive means such as sealing rings, retainers and the like. Typical of all such seals in the needle valves, however is the problem of seal wear. The present seals are compliant or deformable in order to effect the seal against a hard surface and in the conventional valves, the seals are therefore deformed as the seal is effected.
One of the difficulties, therefore, is in the continued deformation of such seals since they tend to become permanently deformed and therefore need to be replaced. Alternatively, such seals are deformed beyond their elastic limits and thereafter lose their resilience through continual deformation and fail to properly seal against the hard surface.
Typical of the prior art valves are shown and described in Bowen et al, U.S. Pat. No. 3,233,863 where a flexible packing ring, such as an O-ring is used to seal against the tapered movable valve member. Also typical of prior art valve seals is Carlson et al, U.S. Pat. No. 3,471,123 where a resilient seat ring seals against a tapered valve member and which is held in position by retainer.